The present invention relates to a method and an apparatus for adjusting the engaged clearance between rotors of a screw compressor comprising a male rotor and a female rotor inside a casing, both of the rotors being rotated, while maintaining a required very small clearance, by means of timing gears fixed individually to the rotors by a shrink fit, and more particularly relates to a method and an apparatus for adjusting the engaged clearance between rotor of a screw compressor for setting a very small clearance between both rotors to a desired value in a short time.
A conventional method of adjusting the clearance between rotors of a screw compressor is disclosed in Japanese Patent Application Laid-Open No. 1-155089, where a very small clearance between the rotors is set using a rotating phase difference between male and female rotors as measured by an encoder or the like, under a condition in which one of the rotors is rotated in forward and backward directions, while the other of the rotors has a braking force applied thereto, under a state in which at least one of the timing gears is removed, which is referred to as a timing adjustment or symmetrizing adjustment.
The setting of a clearance is performed during the assembling process of the screw compressor. Oil hydraulic pressure is applied between one of the timing gears and the rotor on which the one of the timing gears is fixed to loosen the shrink fit between both elements while the movement of the other of the timing gears is being restricted. Then, relative positional displacement is produced between the one of the timing gears and the rotor to which the one of the timing gears is fixed by hitting the tooth surface of the one of the timing gears using a hammer, a shim (thickness gage) is inserted between the rotors to confirm whether the clearance between the rotors is at a required value (shim measurement), and the hammer hitting and the shim measurement are repeated to set the clearance between the rotors to the required value.
In the conventional method described above, there has been a problem in that not only does the shim measurement take a long time, since the setting of the clearance between the rotors (symmetrizing adjustment) is performed by hand, but also the reliability of the symmetrizing adjustment is low, since the accuracy of the symmetrizing adjustment is disturbed by the hammering, which depends on the skill of the worker, leading to rotor hitting or low performance of the compressor as a result.